Fullwidth / Halfwidth Converter
Convert between fullwidth and halfwidth characters. Also supports katakana-hiragana conversion for data cleanup.
What Is Fullwidth/Halfwidth Conversion?
Fullwidth/halfwidth conversion is an online tool that converts between fullwidth and halfwidth characters in text. It's useful for standardizing data entry, normalizing text before form submission, cleaning CSV data, and any situation requiring consistent character widths.
sakutto.ai's fullwidth/halfwidth converter processes everything in your browser — your text is never sent to any server. You can safely convert text containing personal information and business data. Katakana-to-hiragana conversion is also supported.
Batch-convert fullwidth/halfwidth alphanumeric characters, katakana, and symbols, with fine-grained control over what gets converted. Great for normalizing data before database entry, cleaning up directory data, and preprocessing web form inputs. Free, no sign-up required.
How to Use the Fullwidth/Halfwidth & Katakana/Hiragana Converter
Fullwidth ⇔ Halfwidth Conversion
- Select the "Fullwidth ⇔ Halfwidth" tab
- Choose the conversion direction (fullwidth → halfwidth or halfwidth → fullwidth)
- Select what to convert: letters & numbers, katakana, symbols, and/or spaces
- Type or paste your text in the left text area
- The converted result appears in real time on the right
Katakana ⇔ Hiragana Conversion
- Select the "Katakana ⇔ Hiragana" tab
- Choose the conversion direction (katakana → hiragana or hiragana → katakana)
- Type or paste your text in the left text area
- The converted result appears in real time on the right
- Click "Copy" to copy the result to your clipboard
Features of sakutto.ai's Character Converter
- Runs entirely in your browser — your text is never sent to any server
- Fullwidth ⇔ halfwidth and katakana ⇔ hiragana converters in one tool
- Select exactly what to convert: letters & numbers, katakana, symbols, or spaces
- Accurately handles voiced (dakuten) and semi-voiced (handakuten) katakana characters
- Katakana ⇔ hiragana conversion covers small characters (e.g., ァ ⇔ ぁ) too
- Real-time conversion shows results as you type
- One-click copy for the converted result
- Responsive design that works great on smartphones and tablets
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Need to check character counts? Try the Character Counter. Want to compare text differences? Use the Text Diff Checker.
Why Fullwidth/Halfwidth & Katakana/Hiragana Converter on sakutto is safe
Many online tools upload your files to external servers for processing. This tool never sends your text data to any server — everything is processed entirely in your browser.
* Some AI-powered tools require server-side processing. Tools that send data to a server will always notify you beforehand.
| Comparison | Typical online tools | sakutto |
|---|---|---|
| Where data is sent | Uploaded to external servers | Nowhere — processed in your browser |
| Data leak risk | Risk during transfer and server storage | No risk — no network transfer occurs |
| External traffic | File data travels over the internet | No file data appears in network logs |
| Offline use | Not possible (server required) | Works offline after initial load |
How browser-based processing works
- WebAssembly (WASM): Processes text data in your browser at near-native speed. No server communication occurs.
- Web Workers: Runs on a background thread separate from the main thread, so your browser stays responsive during processing.
- After processing, your browser automatically frees the data from memory. No text data remains outside your device.
For IT security teams: How to verify
You can verify that sakutto never sends your text data externally by checking the Network tab in your browser's DevTools while using the tool. You'll see that no requests involving your text data are made. This can also serve as documentation for your IT security team.
Frequently Asked Questions
Is my text sent to a server?
No. All processing happens entirely in your browser, and your text is never transmitted to any external server. You can safely use this tool with confidential content.
Can it convert between katakana and hiragana?
Yes. Switch to the "Katakana ⇔ Hiragana" tab for bidirectional conversion between katakana and hiragana. Voiced marks (dakuten), semi-voiced marks (handakuten), and small characters (ぁ, ぃ, etc.) are all converted accurately.
Are voiced and semi-voiced katakana (e.g., ガ, パ) handled correctly?
Yes. In fullwidth ⇔ halfwidth conversion, halfwidth katakana with voiced/semi-voiced marks use two characters (e.g., ｶﾞ, ﾊﾟ) but are correctly converted. Katakana ⇔ hiragana conversion also handles these accurately (ガ → が, パ → ぱ, etc.).
Can I choose what to convert individually?
Yes. In fullwidth ⇔ halfwidth mode, you can mix and match from four categories: letters & numbers, katakana, symbols, and spaces. In katakana ⇔ hiragana mode, all kana characters are converted at once.
Is the long vowel mark (ー) converted to hiragana?
The long vowel mark "ー" is specific to katakana and has no hiragana equivalent, so it is preserved as-is during katakana-to-hiragana conversion.
Is there a maximum character limit?
There is no hard limit. Typical documents work without any issues. For very long texts, performance may vary depending on your device.
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